﻿// Copyright (c) 2014 Daniel Grunwald
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using Mono.Cecil;
using ICSharpCode.Decompiler.TypeSystem;

namespace ICSharpCode.Decompiler.IL
{
	static class ILTypeExtensions
	{
		public static StackType GetStackType(this MetadataType typeCode)
		{
			switch (typeCode) {
				case MetadataType.Boolean:
				case MetadataType.Char:
				case MetadataType.SByte:
				case MetadataType.Byte:
				case MetadataType.Int16:
				case MetadataType.UInt16:
				case MetadataType.Int32:
				case MetadataType.UInt32:
					return StackType.I4;
				case MetadataType.Int64:
				case MetadataType.UInt64:
					return StackType.I8;
				case MetadataType.IntPtr:
				case MetadataType.UIntPtr:
				case MetadataType.Pointer:
				case MetadataType.FunctionPointer:
					return StackType.I;
				case MetadataType.Single:
					return StackType.F4;
				case MetadataType.Double:
					return StackType.F8;
				case MetadataType.ByReference:
					return StackType.Ref;
				case MetadataType.Void:
					return StackType.Void;
				case (MetadataType)PrimitiveType.Unknown:
					return StackType.Unknown;
				default:
					return StackType.O;
			}
		}

		public static StackType GetStackType(this PrimitiveType primitiveType)
		{
			return ((MetadataType)primitiveType).GetStackType();
		}
		
		public static Sign GetSign(this PrimitiveType primitiveType)
		{
			switch (primitiveType) {
				case PrimitiveType.I1:
				case PrimitiveType.I2:
				case PrimitiveType.I4:
				case PrimitiveType.I8:
				case PrimitiveType.R4:
				case PrimitiveType.R8:
				case PrimitiveType.I:
					return Sign.Signed;
				case PrimitiveType.U1:
				case PrimitiveType.U2:
				case PrimitiveType.U4:
				case PrimitiveType.U8:
				case PrimitiveType.U:
					return Sign.Unsigned;
				default:
					return Sign.None;
			}
		}
		
		/// <summary>
		/// Gets the size in bytes of the primitive type.
		/// 
		/// Returns 0 for non-primitive types.
		/// Returns <c>NativeIntSize</c> for native int/references.
		/// </summary>
		public static int GetSize(this PrimitiveType type)
		{
			switch (type) {
				case PrimitiveType.I1:
				case PrimitiveType.U1:
					return 1;
				case PrimitiveType.I2:
				case PrimitiveType.U2:
					return 2;
				case PrimitiveType.I4:
				case PrimitiveType.U4:
				case PrimitiveType.R4:
					return 4;
				case PrimitiveType.I8:
				case PrimitiveType.R8:
				case PrimitiveType.U8:
					return 8;
				case PrimitiveType.I:
				case PrimitiveType.U:
				case PrimitiveType.Ref:
					return TypeUtils.NativeIntSize;
				default:
					return 0;
			}
		}
		
		/// <summary>
		/// Gets whether the type is a small integer type.
		/// Small integer types are:
		/// * bool, sbyte, byte, char, short, ushort
		/// * any enums that have a small integer type as underlying type
		/// </summary>
		public static bool IsSmallIntegerType(this PrimitiveType type)
		{
			return GetSize(type) < 4;
		}
		
		public static bool IsIntegerType(this PrimitiveType primitiveType)
		{
			return primitiveType.GetStackType().IsIntegerType();
		}

		/// <summary>
		/// Infers the C# type for an IL instruction.
		/// 
		/// Returns SpecialType.UnknownType for unsupported instructions.
		/// </summary>
		public static IType InferType(this ILInstruction inst)
		{
			switch (inst) {
				case NewObj newObj:
					return newObj.Method.DeclaringType;
				case Call call:
					return call.Method.ReturnType;
				case CallVirt callVirt:
					return callVirt.Method.ReturnType;
				case CallIndirect calli:
					return calli.ReturnType;
				case LdObj ldobj:
					return ldobj.Type;
				case StObj stobj:
					return stobj.Type;
				case LdLoc ldloc:
					return ldloc.Variable.Type;
				case StLoc stloc:
					return stloc.Variable.Type;
				case LdLoca ldloca:
					return new TypeSystem.ByReferenceType(ldloca.Variable.Type);
				case LdFlda ldflda:
					return new TypeSystem.ByReferenceType(ldflda.Field.Type);
				case LdsFlda ldsflda:
					return new TypeSystem.ByReferenceType(ldsflda.Field.Type);
				case LdElema ldelema:
					if (ldelema.Array.InferType() is TypeSystem.ArrayType arrayType) {
						var refType = new TypeSystem.ByReferenceType(arrayType.ElementType);
						if (TypeUtils.IsCompatibleTypeForMemoryAccess(refType, ldelema.Type)) {
							return refType;
						}
					}
					return new TypeSystem.ByReferenceType(ldelema.Type);
				default:
					return SpecialType.UnknownType;
			}
		}
	}
}
